Last week, almost 54 percent of Irish voters rejected the treaty, which will govern EU decisionmaking and institutions. That disrupted expectations that the treaty would be concluded by the end of the summer. Now, the Irish government has until October to complete its analysis of the referendum result and present a strategy for future ratification.

"It's not being said specifically yet, but it is quite clear that the other countries, especially Germany and France, want the Irish to vote again," says Simon O'Connor, editor of E!Sharp, a Brussels-based magazine on European Union affairs.

But discussion is under way of the modifications that might be needed to persuade Irish voters to change their minds. A Eurobarometer public opinion survey found that 76 percent of "no" voters believed the negative result would put Ireland in a strong position to negotiate the treaty.

Sinn Féin, the only Irish political party to advocate a no vote, has compiled a list of revisions it would like to see to the treaty. These include workers' rights, protection of public services, and military neutrality.

"Of course the government will say that this list is too ambitious, too detailed, and undeliverable," said Sinn Féin's Caoimhghín Ó Caoláin, a member of the Irish parliament, during a debate on the treaty. "However, already we are hearing from a range of [supportive] voices across the EU, in governments, opposition parties, and social movements."

But Mr. O'Connor, speaking by phone from Brussels, argued that there could be no renegotiation, as that would require a reratification by the 19 countries that have already endorsed it. "Even if you changed one word, it would need reratification," he says.

Instead, Irish voters are likely to be offered clarifying declarations issues that emerged during the referendum campaign, even if some of these are unnecessary.

"Most of the issues that were raised like abortion, neutrality, and corporation tax raised have very little to do with the content of the treaty," says Gavin Barrett, a senior lecturer in law at University College's School of Law in Dublin. But, he says, clear declarations will be needed that maintain Ireland's neutrality as EU members move toward closer military cooperation and that ensure that Ireland's low corporation tax won't be raised as part of French plans for tax harmonization.

"There is also discussion emerging on a reconsideration on the number of [European Commission] commissioners," notes Theresa Reidy of the School of Business and Law at the University College, Cork. In the future, members of the European Commission, the administrative body of the EU, will be rotated between countries instead of giving each country a permanent representative. According to the Eurobarometer survey, this loss of a full-time commissioner was cited as a reason by 6 percent of "no" voters.

"It appears that there is a clause that would let them make that change without the treaty having to be reratified," says Dr. Reidy. "That would be a very significant concession for the Irish government and would also have the support of many other European countries."

Revisiting referendums isn't new to the Irish. In 2001, voters rejected the Nice Treaty, only to pass it a year later in another referendum, when assurances from the EU over the protection of Ireland's neutrality helped to change voters' minds.

Statements from EU leaders have been respectful of the Irish decision and supportive of the government. "The European leaders are careful not to inflame Irish opinion against the European Union," says Reidy. "I don't think there is a crisis in Europe at the moment. But if the Lisbon Treaty was rejected a second time, that would bring about a crisis situation."

"First of all, the [coalition] government is divided," he wrote. "The Eurosceptic prime minister Mirek Topolánek has adopted a very cautious approach and has already commented that the process needs to be slowed down."

In addition, the Constitutional Court's verdict is not expected before the autumn.

Nevertheless, French president Nicolas Sarkozy, who will take over the rotating EU presidency on July 1, is anxious to proceed with ratification in the remaining countries and will visit Ireland next month for talks on how to proceed at the next EU summit in October.

"You could hear very clearly from Sarkozy's press conference [on the first day of the summit] that he wants this treaty to go through," says O'Connor. "He won't accept no for an answer."